M1. The Genetic Material PDF

M1. THE GENETIC MATERIAL - conclusion: DNA passed from type S bacteria into type R, enabling the type R to manufacture the smooth coat necessary for infection Content:...

M1. THE GENETIC MATERIAL - conclusion: DNA passed from type S bacteria into type R, enabling the type R to manufacture the smooth coat necessary for infection Content: Alfred Hershey & Martha Chase 1. History - US microbiologists; used Escherichia coli infected w/ a virus that 2. Deoxyribonucleic acid consisted largely of a protein “head” surrounding DNA 3. Ribonucleic acid - viruses infect bacterial cells by injecting DNA (or RNA) into them and the infected ones produce many more viruses while the viral protein HISTORY coats remain outside bacterial cells Francis Crick - protein – contains sulfur but not phosphorus - co-discoverer with James Watson of 3D DNA structure in 1953 - 35S – radioactive sulfur - “A genetic material must carry out two jobs: (a) duplicate itself, and - nucleic acids – contain phosphorus but not sulfur (b) control the development of the rest of the cell in a specific way” - 32P – radioactive phosphorus - DNA – the only molecule that can fulfill these two - their research proved that DNA is the genetic material and not Friedrich Miescher protein because part of the virus that could enter bacteria to multiply - Swiss physician and biochemist was the part that had phosphorus w/c is the DNA - isolated nuclei from WBCs in pus on soiled bandages Phoebus Levene - nuclein – term used before for the unusual acidic substance - Russian-American biochemist containing nitrogen and phosphorus because the material resided - ribose – a 5-carbon sugar - sugar incell nuclei - 4 nitrogenous bases - nucleic acid – term used now - phosphorus o parts of nucleic acid that are present Archibald Garrod in equal proportions - English physician Erwin Chargaff - first to link inherited disease and protein - Austrian-American biochemist - showed that DNA in several species - noted that people who had certain inborn errors of metabolism did contains equal amounts of ATCG bases not have certain enzymes Maurice Wilkins Frederick Griffith - English physicist - English microbiologist - bombarded DNA w/ X rays using X-ray diffraction technique then - took 1st step in identifying DNA as the genetic material deduced the overall structure of the molecule from the patterns - pneumonia – studied years after 1918 flu pandemic deflected - Streptococcus pneumoniae – one of two types of this was harbored Rosalind Franklin by mice w/ a certain form of pneumonia - English chemist - Type R bacteria – rough in texture; mice injected with this did not - provided a pivotal clue to deducing the 3D structure of DNA develop pneumonia James Watson & Francis Crick - Type S bacteria – smooth because they were enclosed in a - turned attention to the bases; played w/ cardboard cutouts of the 4 polysaccharide capsule DNA bases Oswald Avery, Colin MacLeod, Maclyn McCarty - US physicians; hypothesized that a nucleic acid might be Griffith’s *Watson, Crick, and Wilkins all received the Nobel “transforming principle” Prize, and Franklin did not because she died (the - 1944 – they confirmed DNA transformed the bacteria Nobel can only be awarded to a living person) *  DEOXYRIBONUCLEIC ACID - measured in numbers of base - The DNA double helix is a symbol in modern biology and is found in pairs various forms of art and logos. Kilobase (kb) - DNA's structure is visually appealing but requires an understanding of - stand for a thousand DNA its function for meaningful interpretation. bases - Understanding function necessitates knowledge of structure, forming Megabase (mb) a reciprocal relationship. - stand for a million DNA bases - Chapter goal: Explain DNA structure while considering its role within Gene living cells. - might be 1,400 bases, or 1.4 kb - Genetic material is deoxyribonucleic acid (DNA). long - Genes are fundamental units of heredity, containing DNA that Polynucleotide Chains are Antiparallel Phosphodiester bonds controls body's form and function. - strong attachments formed bet. deoxyribose sugars and phosphates, - Genes are composed of DNA and provide instructions for producing enabling nucleotides to join into long “polynucleotide” chains (align proteins. head to-toe) - Human genes vary in size, ranging from a few hundred DNA bases to Sugar-phosphate backbone over 2 million bases. - created from the attachment Antiparallelism Characteristics of genetic material - opposing orientation of 2 nucleotide chains 1. INFORMATION. The genetic material must contain the information Carbons necessary to construct an entire organism. In other words, it must - of deoxyribose; numbered from 1 to 5, starting with the carbon provide the blueprint to determine the inherited traits of an organism. found by moving clockwise from the oxygen 2. TRANSMISSION. During reproduction, the genetic material must be *One strand of the helix passed from parents to offspring. runs in a 5 prime (5’) to 3 3. REPLICATION. Because the genetic material is passed from parents prime (3’) direction, and to offspring and from mother cell to daughter cells during cell division, the other runs in a 3’ to 5’ it must be copied. direction* 4. VARIATION. Within any species, a significant amount of phenotypic variability occurs. DNA STRUCTURE Gene – a section of DNA molecule whose sequence of building blocks specifies sequence of amino acids in a particular protein Nucleotide – single building block of DNA; consists of 1 deoxyribose sugar, 1 PO4 group, and 1 nitrogenous base Adenine and Guanine - purines (have a 2-ring structure) Thymine and Cytosine - pyrimidines (single-ring structure) Nitrogenous bases - the information-containing parts of DNA because they form sequences DNA sequences Complementary Base Pairing Chromatid A-T & C-G pairing - a chromosome consisting of 1 double helix in unreplicated form; - pairing of a purine with a pyrimidine w/c ensures that the double compacted DNA wrapped at several levels helix has the same width throughout Chromatin Complementary base pairs - ‘colored material’; is not just DNA, it is about 30% histone proteins, - purine-pyrimidine couples 30% scaffold proteins and other proteins that bind DNA, 30% DNA, and Hydrogen bonds 10% RNA - chemical attractions holding DNA base pairs together; attracted to O or N on another molecule DNA Configuration in the Nucleus 14 millimeters long DNA sequence structure forms: - size of smallest DNA if stretched 1. Palindrome or inverted repeats: non annealing DNA sequences 2 micrometers long of the complementary strand that is identical either forward or - size of a chromosome during cell backward annealing DNA sequences of the same strand that is division where DNA is packed into identical. Scaffold proteins The significance is for: - form frameworks that guide DNA strands ▪ Genetic recombination Histones ▪ DNA repair - proteins where DNA coils around on a smaller scale forming ▪ Gene regulation structures that resemble beads on a string ▪ Mutations Nucleosome ▪ Gene regulation* - the DNA ‘bead’; composed of 8 histones (a pair of each of 4 types) ▪ Viral genome organization* + 147 nucleotides of DNA entwined around ▪ DNA Folding and structural variation* ▪ Mobile genetic elements* 2. Mirror repeats: non either forward or backward. Major types of DNA Significance: 1. Genomic DNA/ Nuclear DNA ▪ DNA Replication and repair This compromises the genome of an organism. This genomic DNA is ▪ Gene regulation spread across 46 chromosomes leading to an expression or genetic ▪ Chromosomal traits. The genomic DNA controls various traits of an organism. rearrangements 2. Mitochondrial DNA ▪ Genetic recombination It is located in the Mitochondria. mtDNA is being derived from the ▪ Viral genomes circular bacterial genomes-hence mt-DNA is a double stranded 3. Hairpin: annealing DNA sequences of the same strand. Significance: circular molecule. mtDNA is always maternally inherited. Each ▪ Gene regulation mitochondrion contains about 2 – 10 mtDNA molecules. Unlike ▪ DNA Replication and repair Nuclear DNA, which can undergoe to process of inheritance and ▪ Genetic recombination recombination, mtDNA does not change from parent to offspring ▪ Riboswitches DIFFERENT FORMS OF DNA ▪ Antisense regulation 4. Cruciform: annealing DNA sequences of the both DNA strands ▪ Gene regulation ▪ DNA Replication and repair ▪ Genetic recombination ▪ Chromosomal fragility ▪ Viral genomes ▪ Antibody diversity ▪ Ribosomal RNA Processing 1. B-DNA (Standard DNA): Most common and well-known DNA form. Right-handed double helix with complementary base pairing (A-T, C G). Essential for genetic storage, replication, and transcription. 2. A-DNA:. Right-handed double helix with a slightly different structure than B DNA. a. Inverted repeat Can form under specific conditions and sequences. b. Hairpin Involved in DNA-protein interactions, gene regulation, and structural c. Cruciform diversity. 3. Z-DNA: Left-handed double helix.  Forms in sequences with alternating purines and pyrimidines. bp per turn) is the most predominant, B- form is not observed and left- Associated with gene regulation, transcription, and specific DNA protein handed Z-form (12.4 bp per turn) for conditions with high salinity interactions Features of DNA 1. DNA is double-stranded, so there are two polynucleotide strands alongside each other. 2. The strands are antiparallel, they run in opposite directions. 3. The two strands are wound round each other to form a double helix. 4. The two strands are joined together by hydrogen bond. 5. The bases therefore form base pairs. 6. The base pairs are specific, A only binds to , and C only binds to G 7. These are called complementary base pairs 8. This means that whatever sequence of bases along one strand, the sequence of bases on the other strand must be 9. complementary to it. RIBONUCLEIC ACID ▪ Historical context: - Alexander Rich and David Davies, discovered that the single stranded RNA can be hybridize, and can stick together to form a double-stranded molecule. - Jacob and Monod (1961) first introduced the term mRNA (messenger RNA) - Robert Holley, was the first to demonstrate the structure of a tRNA. ▪ Basic biochemistry of RNA: - It is characterized by presence of 2'-OH in the pentose unit - Uncommon bases: inosine (has the basehypoxanthine), pseudouridine (attached to ribose at C5) Types of RNA - Monocistronic (each mRNA only codes for single polypeptide) for 1. mRNA (messenger RNA) eukaryotes while Polycistronic (each mRNA only codes for - This carries information from the nucleus to the ribosomes which are many polypeptide) for prokaryotes sites of protein synthesis. - The hydrogen and base stacking can also support RNA structure, with - The coding sequence of mRNA determines the amino acid hairpins the most common secondary structure sequence in the protein. - Short base sequences are often found at the end of the hairpins which can - The mRNA is a straight molecule extends from the 5’ to 3’ end. indicate folding of RNA - Product of transcription, its codons guide tRNA for protein synthesis - It can also form non-Watson-Crick molecular binding as guanine can bind - second most abundant RNA among eukaryotes and prokaryotes with uracil and exhibit self-annealing or 2-OH of ribose can bind with other 2. tRNA (transfer RNA) groups - RNAs are generally single-stranded, however in terms of complementary - This RNA is a small chain of about 80 nucleotides. structures- the A form right-handed double-stranded helix (11 - It transfers molecules to the growing polypeptide chains mainly for protein synthesis 3. rRNA (ribosomal RNA) - It is synthesized in nucleolus. - In the cytoplasm, rRNA and a protein, combine and produce ribosomes. The mRNA and the ribosomes combined to produce protein. - The 80% of RNA in the cells are composed of rRNA. - It has two subunits; the small subunit and the large subunit. For eukaryotic cells, there are 4 different kinds of rRNA namely, 28S rRNA, 18S rRNA, 5.8S rRNA, and 5S rRNA.